Carbon dioxide levels in beverages can significantly influence taste and other properties, such as mouthfeel. For this reason carbonation levels usually are carefully monitored during bottling operations. A number of instruments for determining the quantity of carbon dioxide in bottled beverages are commercially available. One common technique involves inserting a probe through the closure of a sealed container (e.g., beverage-filled can or bottle) and transferring a sample of the liquid to a measuring chamber. After the measuring chamber is closed, its volume is expanded via a flexible membrane or a piston-type injector fitted fluid-tight to the chamber. The equilibrium pressure established after the expansion and the sample temperature are then measured. Carbon dioxide content may then be calculated based on Henry's law. Bloder et al. U.S. Pat. No. 6,874,351 describes an instrument adapted to account for dissolved quantities of oxygen and nitrogen so that carbon dioxide levels may be measured more accurately.
Whereas such relatively precise measurement techniques are available for measuring carbonation levels in bottled beverages, these techniques are unsuitable for measuring carbonation levels in beverages in open-atmosphere conditions, such as beverages present in an opened container or which are dispensed from fountain equipment, for example. Techniques for measuring carbonation levels in open-container beverages generally employ a so-called “handshake” method, which involves placing a liquid sample into a measurement vessel and then shaking to achieve equilibrium pressure. The vessel often is equipped with a pressure gauge and thermometer, the readings from which can be used to calculate carbonation levels. Such techniques generally are less precise and less reliable than the aforementioned techniques used in connection with bottled beverages. Errors in measurement may be introduced not only from the equipment used, but also by the individuals making the measurements, including variations in techniques from one operator to the next. It would be desirable to develop a method for more precisely and more reliably measuring carbonation levels in open-container beverages.